The increasing number, density, and power of various advanced control systems within vehicles, and of electric or electromagnetic radiation associated with the communications needs of the advanced information-oriented society, has led to increasing electrical noise in the environment. Pressure, acceleration, and other sensors are mostly configured to amplify fine signals and are thus likely to be affected by this noise. Accordingly, there has been great a demand for improvements in the noise resistance of electronic components for use in automobiles, medical devices and other industrial sensors.
Specific defects in sensors caused by noise include destruction of elements associated with static electricity or overvoltage and malfunctioning of sensor signals induced by radiating or propagating noise. Measures are required to prevent these defects.
For example, as shown in FIG. 7, conventional pressure sensors are structured to prevent radiating and propagating noise. In such pressure sensors, a metal-can-shaped metal cap 64 blocks potential external radiating noise to prevent a pressure sensor chip 61 mounted on a glass pedestal 62 from being affected thereby. Further, a penetrating capacitor 66 of about 1 to 10 nF or the like is mounted in terminal portions (a pressure introducing pipe 63 and a metal stem 65) to remove propagating noise therefrom. With a conventional structure consisting of such a can type package, however, the metal cap 64 and the penetrating capacitor 66 increase the expense of the sensor.
Further, in a conventional pressure sensor consisting of a resin type package as shown in FIG. 8, a metal plate 74 is embedded in an outer case of a resin to protect a pressure sensor chip 71 on a glass pedestal 72 from radiating noise, or a penetrating capacitor is mounted on an external substrate 75 to remove propagating noise from a terminal (socket 76). Even in such conventional case configurations, however, the provision of the additional parts, that is, the metal plate 74 and the penetrating capacitor, increases the expense of the sensor.
Still further, a pressure sensor circuit constructed using a CMOS process requires multiple digital-regulating terminals. In most cases, these terminals are connected to an external device by wire bonding, and thus act as paths through which extraneous noise may enter the sensor, thereby degrading noise resistance capability.
It would therefore be desirable to provide a semiconductor physical quantity sensor that can, at relatively modest expense, provide significantly improved resistance to extraneous noise.